Such drills can withstand heating to several hundred degrees without the soldering becoming soft and the carbide plate loosening.Ī new trend for very heavy hammer drills (over 5 kg) is mono-block cutting (solid carbide head): here a solid carbide body is butted to the drill shaft and thermally attached, e.g. ![]() The trend here was towards high-temperature restoration soldering at over 1,000 degrees. After cooling, the connection is then solid. The cutting body made of 'hard metal' (tungsten carbide.), usually in the form of a small platelet, is inserted into the prepared grooves of the drill shaft and surrounded there with liquid metal (brass or bronze solder). must be joined together, and this is usually done by soldering. so even "five-edge bits" are actually only highly modified 2-edge bits! Some suppliers even advertise more edges than are actually there- somehow the bit's tip is considered and sold as a separate cutting edge. The cross-shaped 4-edge bit is still popular, but it is not really 'genuine,' because two of the four cutting edges are wider and longer and they are the ones cutting and hammering, while the other two only support the drilling process as secondary/minor cutting edges and do very little on the borehole wall. Four crosswise-arranged cutting edges - this was too much friction! The remainders of these first 4-edgers still float around today on the internet as "special deals" in various online shops. When the '3-edge bit' came, there were no obvious negative effects, but with the 4-edge- definitely! The professionals on the construction sites of tunnels, high-rises, etc., which drill hundreds of holes every day, rejected the new drill quickly. 3 edges use more energy, generate more friction and warmth, and become susceptible to overheating, thus wearing down faster. But, it's not so simple! 2-edge drill bits still bore fastest! That's because the more edge surfaces a drill has, the slower it becomes. ![]() Yes, the number of cutting edges on a drill bit plays a big role, at least in drill advertisements which have the motto: "the more edges, the better." According to this logic, the classic 2-edge bit which looks like a percussion drill falls far behind the 3-edge bits and is thought of as inferior.
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